The patch titled Subject: [PATCH 2 of 4] hotplug-memory: adding non-section-aligned memory is bad has been added to the -mm tree. Its filename is hotplug-memory-adding-non-section-aligned-memory-is-bad.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/SubmitChecklist when testing your code *** See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find out what to do about this The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/ ------------------------------------------------------ Subject: Subject: [PATCH 2 of 4] hotplug-memory: adding non-section-aligned memory is bad From: Jeremy Fitzhardinge <jeremy@xxxxxxxx> Adding non-section-aligned memory will cause bad results, because page structures are only built on section-aligned boundaries. Also, memory whose size isn't a multiple of the section size is silently ignored. This patch adds a couple of WARN_ONs to help confused programmers work out what's going wrong when they hotplug memory without being aware of these constraints. Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> Cc: Yasunori Goto <y-goto@xxxxxxxxxxxxxx> Cc: Christoph Lameter <clameter@xxxxxxx> Cc: Dave Hansen <dave@xxxxxxxxxxxxxxxxxx> Cc: Ingo Molnar <mingo@xxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- include/linux/mmzone.h | 3 +++ mm/memory_hotplug.c | 5 +++++ 2 files changed, 8 insertions(+) diff -puN include/linux/mmzone.h~hotplug-memory-adding-non-section-aligned-memory-is-bad include/linux/mmzone.h --- a/include/linux/mmzone.h~hotplug-memory-adding-non-section-aligned-memory-is-bad +++ a/include/linux/mmzone.h @@ -829,6 +829,9 @@ static inline unsigned long early_pfn_to #define PAGES_PER_SECTION (1UL << PFN_SECTION_SHIFT) #define PAGE_SECTION_MASK (~(PAGES_PER_SECTION-1)) +#define SECTION_SIZE (1UL << SECTION_SIZE_BITS) +#define SECTION_SIZE_MASK (SECTION_SIZE - 1) + #define SECTION_BLOCKFLAGS_BITS \ ((1UL << (PFN_SECTION_SHIFT - pageblock_order)) * NR_PAGEBLOCK_BITS) diff -puN mm/memory_hotplug.c~hotplug-memory-adding-non-section-aligned-memory-is-bad mm/memory_hotplug.c --- a/mm/memory_hotplug.c~hotplug-memory-adding-non-section-aligned-memory-is-bad +++ a/mm/memory_hotplug.c @@ -301,6 +301,11 @@ int add_memory_resource(int nid, struct u64 start = res->start; u64 size = res->end - res->start + 1; + /* Adding non-section-aligned memory will give unexpected + and unintuitive results. */ + WARN_ON((start & SECTION_SIZE_MASK) != 0); + WARN_ON((size & SECTION_SIZE_MASK) != 0); + if (!node_online(nid)) { pgdat = hotadd_new_pgdat(nid, start); if (!pgdat) _ Patches currently in -mm which might be from jeremy@xxxxxxxx are origin.patch git-x86.patch sparsemem-vmemmap-does-not-need-section-bits.patch kbuild-create-a-way-to-create-preprocessor-constants-from-c-expressions.patch pageflags-use-an-enum-for-the-flags.patch pageflags-get-rid-of-flags_reserved.patch pageflags-introduce-macros-to-generate-page-flag-functions.patch pageflags-convert-to-the-use-of-new-macros.patch pageflags-use-proper-page-flag-functions-in-xen.patch pageflags-eliminate-pg_xxx-aliases.patch hotplug-memory-add-add_memory_resource.patch hotplug-memory-adding-non-section-aligned-memory-is-bad.patch sparsemem-reduce-i386-pae-section-size.patch paravirt_ops-dont-steal-memory-resources-in-paravirt_disable_iospace.patch xen-make-blkif_getgeo-static.patch -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html